You can issue a partial refund, full refund, or add an additional charge to an order from either the Owner tablet or the Owner Dashboard.
From the Owner tablet:
Find the ticket on Orders or Transactions
Select it, and you will have 3 options; Print, Add Charge & Refund
When it comes to Refunds, they can pick a number, or the Full Refund option
From the Owner Dashboard:
On the Owner Dashboard, click Restaurant
Click on Orders
Find the Order and click on it
Click on either Add Refund or Add Charge at the top
Enter the amount and submit